The present invention relates to an electrical test probe tip capable of establishing an electrical connection to test objects on a circuit board and particularly to rounded or irregularly shaped test objects.
Typical modern circuit boards tend to include a variety of components (hereinafter referred to generally as “circuit board components”). For example, most circuit boards will include one or more integrated circuits with a set of leads, legs, or pins (hereinafter referred to as “leads”) on both sides of a package. There are also many rounded or irregularly shaped devices such as ceramic resistors, capacitors, through hole pins. Circuit board components such as those described above often need to be monitored or tested by testing instruments such as oscilloscopes and other measuring, monitoring, diagnostic, and signal processing instruments.
Electronic test probes are used to provide an electrical connection between circuit board components and testing instruments. An electronic test probe generally consists of a probing head, a cable, and a connector. The probing head may have an integral or replaceable probing tip that is suitable for making an electronic contact with electrical components. The probing head is attached to a first end of the cable and the connector is attached to the opposite end of the cable.
As shown in FIG. 1, a conventional test probe tip is generally in the shape of a cone that narrows, similar to the point of a pencil, becoming a sharp point or slightly blunt point. Test probe tips are usually made out of conductive metal such as copper, beryllium copper, nickel-palladium alloy, metal alloy, aluminum, steel, or a similar conductive metal.
Test probes that are used manually require an operator to hold the test probe tip against the circuit board components. Conventional test probe tips having a single point can easily slip off circuit board components, especially rounded or irregularly shaped ones. After slipping off a circuit board component, the exposed conductive material on a conventional test probe tip may, for example, contact two leads at the same time, cause an electrical short, and possibly damage the component.
Approaches have been taken in the past to solve the problems of a conventional test probe tip slipping and contacting two leads at the same time, causing an electrical short.
U.S. Pat. No. 4,783,624 to Sabin (the “Sabin reference”) sets forth a contact probe device and, as an example of an alternative to common conical pointed tips, a test probe tip with a “V” cut. As shown in the Sabin reference, the wide portion of the V starts from the outer periphery of the first end of the tip and the narrow portion of the V meets at the center longitudinal planar axis toward the second end. The Sabin contact tip essentially creates two contact points instead of one. These points are unsteady and would tend to slip almost as easily as a single tip. This is a particular problem created with testing rounded or irregularly shaped leads or circuit board components. Further, the Sabin contact tip's design requires that most or all of the tip be exposed conductive material in order to establish good electrical contact with the contact points. The amount of exposed conductive material increases the chance for a short to occur. Finally, the probe tip with a “V” cut would be difficult to create and expensive to produce.
U.S. Pat. No. 5,731,710 to Mizuno et al. sets forth several test probe tips (the “Mizuno tips”) that have sharp edges particularly suited for breaking through a surface of a test member so as to establish an electrical connection. In several of the embodiments, a plurality of slits extends radially and axially from a top center of the tip. Although the slitted embodiments of the Mizuno tips would be well suited to probing through hole pins, they would be poorly suited to probing components that are rounded or irregularly shaped. Further, the Mizuno tips appear to have an exterior surface that is exposed conductive material and, therefore, would increase the chance for a short to occur. Finally, the Mizuno slitted tips would be difficult to create and expensive to produce.
U.S. Pat. No. 5,557,213 to Reuter et al. sets forth a spring-loaded electrical contact probe having a tip that has a locking attachment that includes at least one slot and at least one flange. The primary purpose of the slot and flange appear to relate to the locking feature of the locking attachment.